The University Record, May 8, 1995
By Sally Pobojewski
News and Information Services
By re-creating a way of life that vanished from the Great Lakes thousands of years ago, a U-M paleontologist has demonstrated how PaleoIndians living in the region at the end of the last Ice Age preserved meat from large animal kills by storing it underwater.
"Underwater caching turns out to be a simple and effective way to store meat for long periods. Fossils preserved at ancient cache sites suggest it was an important and common part of the winter-to-spring subsistence strategy of Ice Age hunters," says Daniel C. Fisher, professor of geological and biological sciences and curator of the Museum of Paleontology. Fisher presented results of his experiments at the Society for American Archaeology meeting in Minneapolis last week.
Evidence of butchery and underwater meat caching by Ice Age hunters in North America was first discovered by Fisher in the late 1980s while he was excavating an 11,000-year-old mastodon found at the Heisler site in southern Michigan. Other examples of butchered mastodons were later discovered in Ohio, Indiana, Michigan and New York.
Mastodons roamed the North American continent for millions of years until they suddenly died out approximately 10,000 years ago--soon after bands of PaleoIndians began moving across North America from Siberia via the Bering land bridge. This coincidental timing has led some paleontologists to believe that the animals were hunted to extinction, while others maintain climate change was responsible.
"In order to resolve the hunting-vs.-climate extinction debate, we needed to know more about PaleoIndian subsistence patterns," Fisher says. "We had many unanswered questions. Is it possible for small groups of hunters working with stone tools to quickly butcher a large animal and store the meat in a shallow pond? How long will the meat remain edible and what changes does it undergo?"
Fisher's experiments to test the viability of underwater meat preservation began in 1989 in the U-M's E.S. George Reserve near Hell, Mich. From autumn to mid-winter, Fisher anchored legs of lamb and venison on the bottom of a shallow, open-water pond and buried other meat sections in a nearby peat bog. Caches were left in place for up to two years and checked periodically for decomposition.
"The meat remained essentially fresh for most of the first winter," Fisher said. "By spring, progressive discoloration had developed on the outside, but interior tissue looked and smelled reasonably fresh."
The combination of cold water temperature and increased acidity in the meat produced by pond bacteria called lactobacilli, which can survive without oxygen, made the meat unpalatable to other bacteria that normally decompose dead tissue, according to Fisher. Laboratory analyses of meat retrieved from the pond and bog in April 1992 showed no significant pathogens and bacterial counts were comparable to levels found in control samples Fisher stored in his home freezer.
On Feb. 13, 1993, the body of a 28-year-old draft horse, which died the previous day of natural causes, was donated to Fisher for use in his research. Using simple stone tools he made himself and replicating techniques documented at mastodon excavation sites, Fisher and two colleagues butchered the horse and placed sections of meat in the pond through a hole chopped in the ice. "The stone tools were very effective," Fisher says. "For some procedures, especially the skinning process, they worked better than steel knives."
Fisher monitored the condition of the meat at two-week intervals throughout the following summer. "As long as ice remained on the pond, the meat stayed essentially fresh," Fisher says. "By June, the meat had developed a strong smell and sour taste, but still retained considerable nutritive value."
In future research, Fisher hopes to use signs of meat caching and butchery by humans, together with growth records preserved as "tree-ring-like" features in teeth, to trace the effects of human hunting.
"Once we can identify animals killed by humans, we can use information on these animals' age and gender--determined by examining their skeletons and tusks--to model the probable effects of human predation on mastodon populations," he says. "This will help us answer the ultimate question of what caused the mastodon's extinction."
Fisher's research on mastodon and mammoth extinctions is supported by a grant from the National Science Foundation.